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Evidence for a Double-Stranded Circular DNA Genome in a Second Group of Plant Viruses. B. E. L. Lockhart, Department of Plant Pathology, University of Minnesota, St. Paul 55108; Phytopathology 80:127-131. Accepted for publication 22 June 1989. Copyright 1990 The American Phytopathological Society.. DOI: 10.1094/Phyto-80-127.

Evidence based on nuclease sensitivity, buoyant density, electron microscopy, and molecular cloning indicates that certain small nonenveloped bacilliform plant viruses may constitute a second group of viruses of higher plants having a circular double-stranded DNA genome. Purified bacilliform virions of Commelina yellow mottle virus (CoYMV) contain double-stranded DNA molecules 7.3 kilobase pairs (kbp) in size, 2.1-2.3 ?m in length, with a buoyant density of 1.57 g/cm3 in CsCl-ethidium bromide gradients. DNA extracted from CoYMV virions consists of linear and circular forms, which migrate separately in agarose gels. CoYMV genomic DNA appears to have two single-stranded discontinuities and was not shown to be infectious. Preliminary data on three other viruses similar to CoYMV in size and morphology?banana streak virus (BSV), canna yellow mottle virus (CaYMV), and Kalanchoe top-spotting virus (KaTSV)?indicate that they also contain double-stranded DNA of similar size. These plant viruses are of potential interest for use as vectors for gene transfer in higher plants.